The present invention relates to a stripper packer which is designed to pack-off around coiled tubing being stripped in and out of a well bore.
A stripper packer is used to pack-off around coiled tubing being stripped in and out of a well bore. A stripper packer consists of a main body having a first end and a second end. A passage extends from the first end to the second end, through which coiled tubing passes when being stripped in and out of a well bore. An annular sealing element is provided which encircles the passage. A piston is provided to directly or indirectly apply a compressive force to the annular sealing element. When subjected to a compressive force, the annular sealing element expands inwardly to form a circumferential seal around the coiled tubing. Of course, when the annular sealing element becomes worn the stripper packer is no longer capable of providing an effective seal.
What is required is a stripper packer that has a backup seal which can be used should the annular sealing element become worn and no longer be capable of providing an effective seal.
According to the present invention there is provided a stripper packer which includes a main body having a first end and a second end. A passage extends through the main body from the first end to the second end, thereby facilitating the passage of coiled tubing through the main body when the coiled tubing is being stripped in and out of a well bore. A primary sealing element encircles the passage. A secondary sealing element encircles the passage. A piston is positioned within the main body. Movement of the piston in a first direction toward the first end of the main body applies a compressive force to the primary sealing element thereby causing the primary sealing element to expand inwardly to form a circumferential seal around the coiled tubing. Movement of the piston in a second direction toward the second end of the main body applies a compressive force to the secondary sealing element thereby causing the secondary sealing element to expand inwardly to form a circumferential seal around the coiled tubing.
The stripper packer, as described above, has a built in secondary sealing element when the primary sealing element is no longer effective, the secondary sealing element can be activated to take over the sealing function by merely moving the piston which activates the primary sealing element in the opposite direction.
Although beneficial results may be obtained through the use of the stripper packer, as described above, a preferred configuration involves the use of a pressure member positioned between the primary annular element and the secondary sealing element. The piston is coupled to the pressure member so that movement of the piston in the first direction pulls the pressure member toward the first end of the main body exerting a compressive force upon the primary sealing element thereby causing the primary sealing element to expand inwardly to form a circumferential seal around the coiled tubing. Movement of the piston in a second direction pushes the pressure member toward the second end of the main body exerting a compressive force upon the secondary sealing element thereby causing the secondary sealing element to expand inwardly to form a circumferential seal around the coiled tubing.
Although beneficial results may be obtained through the use of stripper packer, as described above, when the primary sealing element fails it must be replaced. Removal of the stripper packer from the wellhead for replacement of the primary sealing element results in down time for the well. Even more beneficial results may, therefore, be obtained when the primary sealing element is replaceable in situ. According to this aspect of the invention the main body has a primary seal access connection which provides access to the primary sealing element. The primary seal access connection is capable of being separated while the main body is positioned on a wellhead with coiled tubing extending through the passage, thereby permitting the primary sealing element to be removed from the main body and replaced without removing the main body from the wellhead.
Although beneficial results may be obtained through the use of the stripper packer, as described above, eventually the secondary sealing element will also show signs of wear. Even more beneficial results may, therefore, be obtained when the secondary sealing element is also replaceable in situ. According to this aspect of the invention the main body has a secondary seal access connection which provides access to the secondary sealing element. The secondary seal access connection is capable of being separated while the main body is positioned on a wellhead with coiled tubing extending through the passage, thereby permitting the secondary sealing element to be removed from the main body and replaced without removing the main body from the wellhead.